R3303-HP HSR6800 Routers Layer 3 - IP Routing Configuration Guide
157
Configuring IS-IS GR
Restarting IS-IS on a router will cause network disconnections and route reconvergence.
With the GR feature, the restarting router (known as the "GR restarter") can notify the event to its GR
capable neighbors. GR capable neighbors (known as "GR helpers") keep their adjacencies with the
router within a configurable GR interval. After the restart, the router contacts its neighbors to retrieve its
routing table.
During this process, the network keeps stable.
The IS-IS GR and IS-IS NSR features are mutually exclusive.
To configure GR on the GR restarter and GR helper:
Ste
p
Command
Remarks
1. Enter system view.
system-view N/A
2. Enable IS-IS and
enter IS-IS view.
isis [ process-id ] [ vpn-instance
vpn-instance-name ]
Disabled by default.
3. Enable the GR
capability for IS-IS.
graceful-restart Disabled by default.
4. Set the Graceful
Restart interval.
graceful-restart interval timer
300 seconds by default.
The Graceful Restart interval is set as the
holding time in the hello PDUs. Within the
interval, the neighbors will keep their
adjacency with the GR restarter.
5. Suppress the SA bit
during restart.
graceful-restart suppress-sa
Optional.
By default, the SA bit is not suppressed.
By enabling the GR restarter to suppress the
Suppress-Advertisement (SA) bit in the hello
PDUs, the neighbors will still advertise their
adjacency with the GR restarter.
Configuring IS-IS NSR
According to the GR feature, after an active/standby MPU switchover in standalone mode or a global
active/standby MPU switchover, the GR restarter obtains routing information from its neighbors, and the
IS-IS process must learn all routes. If the network topology has changed during the switchover period,
removed routes cannot be updated to the device, which might cause blackhole routes.
NSR solves the problem in the follow way:
• In standalone mode, NSR backs up IS-IS link state information from the active MPU to the standby
MPU. After an active/standby MPU switchover, NSR can complete link state recovery and route
regeneration without requiring the cooperation of other devices.
• In IRF mode, NSR backs up IS-IS link state information from the global active MPU to the global
standby MPU. After a global active/standby MPU switchover, NSR can complete link state recovery
and route regeneration without requiring the cooperation of other devices.
The IS-IS NSR and IS-IS GR features are mutually exclusive.